1. Field of the Invention
The present invention relates to a wear-resistant coated member. More particularly, the invention relates to a wear-resistant coated member having an aluminum alloy with excellent wear resistance as a coating layer, comprising aluminum (Al) and silicon (Si) as main constituent components, Al matrix and 3% by weight or more of Si form solid solutions, and if required and necessary, further comprising at least one additional component selected from the group consisting of magnesium (Mg), copper (Cu), tin (Sn), lead (Pb); elements of IV group (for example, titanium (Ti), zirconium (Zr), hafnium (Hf)), elements of VA group (for example, vanadium (V), niobium (Nb), tantalum (Ta)), elements of VI group (for example, chromium (Cr), molybdenum (Mo), tungsten (W)), elements of VII group (for example, manganese (Mn)), elements of VIII to X groups (for example, iron (Fe), cobalt (Co), nickel (Ni)), and the like, in the Periodic Table.
2. Description of the Related Art
Conventionally, castings made of Al--Si alloy materials (for example, AC3A, AC8A to C, AC9A to B, or the like) containing about 10 to 20% by weight of Si have been known as products comprising a wear-resistant aluminum alloy material. However, since those aluminum alloys are produced by casting, primary crystal particles of Si which contributes to improvement of wear resistance have considerably large particle size of 20 to 150 .mu.m, and the amount of Si is not sufficient. As a result, the necessary wear resistance can not be obtained. Further, if Si amount in the alloy material is further increased in order to improve wear resistance of cast products obtained from the alloy materials, casting properties deteriorate, and machinability of cast products are extremely decreased. Thus, there are problems on practical use. For this reason, a powder extrusion method, sintering method, spray coating method, or the like is mainly used in the production of such an alloy in order to obtain Al--Si alloy having an increased Si amount.
Japanese Patent Publication (Laid-open) No. Hei 2-70036 (hereinafter refer to JP-A-) describes a wear-resistant aluminum alloy containing 5 to 35% by weight of Si. This alloy is produced by sintering a starting material powder, (followed by cold press molding and hot press molding), and then hot extrusion. The starting material powder used is a rapidly solidified powder produced by using, for example, a gas atomizing method.
JP-A-53-68611 describes a process for producing an aluminum alloy by spray coating, which comprises a step of spray coating an aluminum alloy having eutectic phase on a substrate at normal temperature or lower, and a step of conducting heat treatment at a temperature at which grain boundary between particles of the spray coated metal disappears, or more. This process yields an aluminum alloy comprising, Si 8 to 25 wt %, Mg 0.1 to 6 wt %, Cu 0.5 to 5 wt %, and the remainder being substantially Al wt %.
Where the powder extrusion method is used, an aluminum alloy having further fine Si particles (average particle size: about 10 .mu.m) is obtained as compared with the case of using the casting method. However, this aluminum alloy does not have sufficient wear resistance. According to the production process as described in JP-A-2-70036, the production (processing) cost is increased as compared with the casting method. Further, the Si amount in Al--Si alloy is at most 35% by weight, and further increasing the Si amount remarkably impairs the workability.
The spray coating method, for example, as described in JP-A-53-68611, attempts to improve wear resistance by spray coating an aluminum alloy containing about 8 to 25% by weight of Si on a substrate to form a layer having Si solid solution in supersaturation, and heat treating it to precipitate eutectic Si phase finely. However, the aluminum alloy obtained by this process contains a small Si amount, and since the alloy is subjected to heat treatment at 400.degree. C. or more, hardness is decreased. Thus, wear resistance is not sufficient in this alloy. Further, this alloy has various problems on production and also productivity such that heat treatment is necessary after spray coating.
As described above, the aluminum alloy obtained by casting method has a large average particle size of Si, so that a sufficient wear resistance cannot be obtained. Further, the alloy obtained using the conventional spray coating method contains a small Si amount, and the wear resistance cannot be improved unless heat treatment is conducted after spray coating. Even in the aluminum alloy having fine Si particle size obtained using the powder extrusion method, hardness Hv is about 180, and thus the wear resistance is not sufficient.